The parent and radical-modified chitin units are computationally studied and the parent chitin unit possesses closed-shell singlet(CS)state as its ground state.Two radicals(CH_(3)·and CH_(3)CH_(2)·)are chose...The parent and radical-modified chitin units are computationally studied and the parent chitin unit possesses closed-shell singlet(CS)state as its ground state.Two radicals(CH_(3)·and CH_(3)CH_(2)·)are chosen to modify the parent chitin unit.Calculations predict that CH_(3)CH_(2)·-modified chitin unit possesses the open-shell broken-symmetry(BS)singlet diradical ground state,different from that CH_(3)·-modified chitin unit is a triplet diradical.That is to say,the magnetic conversion can occur from nonmagnetic exchange coupling to antiferromagnetic(AFM)or ferromagnetic(FM)exchange coupling by means of the radical modification method.The present work helps to get a basic understanding of structures and electronic properties of chitin and its radical-modified derivatives at the atomistic level.Moreover,it also provides a feasible way to design new chitin-based magnetic materials and organic magnetic switches.展开更多
The polarizability(α) and second hyperpolarizability(γ) were systemically investigated for singlet diradical complex involving X(X=B,Al,Ga) atom.The results show that both the α and γ can be effectively tune...The polarizability(α) and second hyperpolarizability(γ) were systemically investigated for singlet diradical complex involving X(X=B,Al,Ga) atom.The results show that both the α and γ can be effectively tuned by varying the distance R(between compound A and a water molecule) and acceptor atom X.The lone pair of electrons from the O atom of the water molecule entered into the vacant p orbital of atom X,which increased the diradical character and led to the increase of the α and γ values.Furthermore,the polarizable continuum model(PCM) was used to test the effects of H2O and CCl4 solvents on the α and γ values.Both the α and γ values of the studied diradical complex 1a(1b,1c) in H2O and CCl4 were uniformly enhanced.And the solvent effects of H2O on either α or γ were larger than those of CCl4.展开更多
Knowledge about electronic structures is important to gain an understanding of the unique functional properties of diradicaloids.In this study,we synthesized and characterized a diradicaloid in which two phenalenyl ra...Knowledge about electronic structures is important to gain an understanding of the unique functional properties of diradicaloids.In this study,we synthesized and characterized a diradicaloid in which two phenalenyl radical sites are coupled antiferromagnetically via a through-space interaction.The results of quantum chemical,physicochemical(^(1)H NMR,electronic absorption,cyclic voltammetry,SQUID,ESR),and chemical reactivity studies show that this diradicaloid has singlet diradical character.An assessment of the nature of the bonding interaction between two radical sites in this species using DFT calculations demonstrates that a small spatial overlap between the two SOMOs in this diradicaloid provides an efficient electron exchange path for the singlet state to be substantially lower in energy than the triplet state.展开更多
Organic diradicaloids have unusual open-shell nature and properties and are promising materials for organic electronics,spintronics,energy storage and nonlinear optics.In this review,we focus on indeno-type organic di...Organic diradicaloids have unusual open-shell nature and properties and are promising materials for organic electronics,spintronics,energy storage and nonlinear optics.In this review,we focus on indeno-type organic diradicaloids and summarize their molecular design and synthesis,as well as topological structures,open-shell characters and diradical properties.The molecular systems are classified into indenofluorenes and diindenoacenes,indeno-based molecules with one-dimensional,two-dimensional and unique topological structures,and heterocyclic indeno-based molecules.By constructing these various topologicalπ-skeletons with tunable conjugation modes and variation of atomic composition,their key open-shell parameters,such as diradical characters and singlet-triplet energy gaps,along with the optical,electronic and magnetic properties,as well as stabilities are efficiently modulated.More attention may be paid to accurate computational analysis,rational design and synthesis,and novel functions of indeno-type diradicaloids,which will promote the development of radical chemistry and materials.展开更多
Organic radicals with unpaired electrons have shown great semiconducting properties with potential applications in the field of organic photodetectors,organic light-emitting diodes and organic spintronics.A major prob...Organic radicals with unpaired electrons have shown great semiconducting properties with potential applications in the field of organic photodetectors,organic light-emitting diodes and organic spintronics.A major problem for limiting radicals from laboratory research to practical applications is the relatively low chemical and physical stabilities.Therefore,the right selection of radical core is the key to meaningful scientific research.Phenoxyl radical is one of the few stable radicals with spin distribution properties.Moreover,phenoxyl diradicals provide extract stability due to multiple resonance structures.Due to the long-distance spin distribution,which makes phenoxyl diradicals show interesting electronic and magnetic properties.In this review,we summarize the progress of phenoxyl diradicals in recent years in terms of syntheses,properties and future perspective.展开更多
Two-electron oxidations of three 1,2-di(bisphenylamino)-benzenes afforded a class of nitrogen analogues of o-quinodimethane. Their elec-tronic structures in the ground state were studied by spectroscopic techniques ...Two-electron oxidations of three 1,2-di(bisphenylamino)-benzenes afforded a class of nitrogen analogues of o-quinodimethane. Their elec-tronic structures in the ground state were studied by spectroscopic techniques including EPR and UV-vis absorption spectroscopy. They have open-shell singlet ground states with thermally accessible triplet states. One of them (12+2) has been crystalized and isolated. SQUID measurements, single crystal X-ray diffraction and theoretical calculat ons show I has unexpected non-Kekule diradical character, sharply different from o-quinodirnethane.展开更多
By using weakly coordinating anions we succeeded in the stabilization and isolation of two Würster's blue-based diradicaloid dications with saturated spacers. Their geometries and electronic structures were i...By using weakly coordinating anions we succeeded in the stabilization and isolation of two Würster's blue-based diradicaloid dications with saturated spacers. Their geometries and electronic structures were investigated by various experiments in conjunction with DFT calculations. Both one-dimensional alkylate-bridged dications show considerable diradical character with spacer-dependent singlet-triplet energy gaps. One of them displays a much enhanced diradical character and could basically be viewed as a pure diradical with degeneracy of singlet and triplet states.展开更多
Air stable diradicaloid polycyclic aromatic hydrocarbon(PAH)materials possess unique electronic and magnetic properties for various applications.In general,long conjugated distances between two radical centers are req...Air stable diradicaloid polycyclic aromatic hydrocarbon(PAH)materials possess unique electronic and magnetic properties for various applications.In general,long conjugated distances between two radical centers are required to improve the air stability,thereby complicating the synthetic procedures.Herein,the chalcogen containing rubicenes(O-,S-,and Se-rubicenes)were systematically investigated to understand the chalcogen effects on chalcogen-rubicene physicochemical properties.Impressively,these rubicenes presented unprecedented diradical characterwithin one simple benzene ring and excellent air stabilities.Theirdiradicalcharacterweremanifested by single-crystal X-ray studies,variable-temperature nuclear magnetic resonance,and electron spin resonance.Furthermore,the nucleus independent chemical shifts andthe anisotropy of the induced currentdensity calculations revealed that the formation of diradical was caused by a pro-aromaticity driving force.Importantly,the diradical character of rubicenes are visualizedbyFractionalOccupationNumberWeighted Electron Density(FOD)plots,which present high NFOD values from 1.651 to 1.830.This contribution provided distinctive insights into the structure and property relationship of PAH diradicals.展开更多
The mechanism of photocycloaddition reaction between 6-azauracll and acetone was studied by using semiemptrical SCFMO AMI method. It was found that this reaction is not a concerted one. The calculated results are as f...The mechanism of photocycloaddition reaction between 6-azauracll and acetone was studied by using semiemptrical SCFMO AMI method. It was found that this reaction is not a concerted one. The calculated results are as follows:(1) A T1 state exciplex is on the T1 state energy surface; (2) T exciplex as a reactant will proceed along the energy surface of T1 state to form a diradical intermediate. The energy barrier of this reaction step is 63. 6 kJ/mol; (3) The T1 state diradical intermediate happens to be close in energy to the ground state intermediate with a similar geometry. Such a situation turns out to be very favorable for an intersystem crossing (jump from the T, state to the ground state) ; (4) The final product will be formed from the ground S0 state intermediate via an energy barrier 88. 2 kJ/mol.展开更多
Recent years have witnessed breakthroughs in the study of zigzag hydrocarbon belts.However,the synthesis of heterocycle-containing zigzag molecular belts remains very rare and challenging despite their interesting str...Recent years have witnessed breakthroughs in the study of zigzag hydrocarbon belts.However,the synthesis of heterocycle-containing zigzag molecular belts remains very rare and challenging despite their interesting structures and potential applications in chemistry and materials science.Here,we report the expeditious construction of a highly strained belt[4]arene[4](1,4-dihydropyridine)structure using the fjords-stitching strategy.The synthesis comprised four-fold abnormal m-bromination of four Npivaloylaniline units and Pd_(2)(dba)_(3)/4-Me_(2)NC_(6)H_(4)Pt Bu_(2)-catalyzed intramolecular C-N bond-forming reactions.Subsequent functionalization through Narylations produced a variety of tetraza-embedded octahydrobelt[8]arenes.Further oxidation of p-methoxyphenyl-substituted belt[4]arene[4](1,4-dihydropyridine)with Ag[Al(O^(t)Bu^(F))^(4)]yielded a singlet diradical dication N-doped zigzag belt.展开更多
An unexpected bistricyclic aromatic ene AF was synthesized in a tin(Ⅱ)chloride-mediated reductive aromatization reaction.The obtained AF showed a highly overcrowded structural conformation as revealed by X-ray crysta...An unexpected bistricyclic aromatic ene AF was synthesized in a tin(Ⅱ)chloride-mediated reductive aromatization reaction.The obtained AF showed a highly overcrowded structural conformation as revealed by X-ray crystallography.Interestingly,AF exhibited reversible high-contrast mechanochromism and thermochromism between pale and red color.The obvious chromism is likely ascribed to the conformation transformation and trace amount of diradical species formation upon stimulus.展开更多
The block correlated coupled cluster (BCCC) method, with the complete active-space self-consistent-field (CASSCF) reference function, has been applied to investigating the singlet-triplet gaps in several substituted c...The block correlated coupled cluster (BCCC) method, with the complete active-space self-consistent-field (CASSCF) reference function, has been applied to investigating the singlet-triplet gaps in several substituted carbenes including four halocarbenes (CHCl, CF2, CCl2, and CBr2) and two hydroxycar-benes (CHOH and C(OH)2). A comparison of our results with the experimental data and other theoretical estimates shows that the present approach can provide quantitative descriptions for all the studied carbenes. It is demonstrated that the CAS-BCCC method is a promising theoretical tool for calculating the electronic structures of diradicals.展开更多
Homogeneous formation of polychlorinated dibenzothiophenes/thianthrenes(PCDT/TAs),sulfurated compounds analogous to polychlorinated dibenzo-p-dioxin/dibenzofurans(PCDD/Fs), has been well-documented to occur via ra...Homogeneous formation of polychlorinated dibenzothiophenes/thianthrenes(PCDT/TAs),sulfurated compounds analogous to polychlorinated dibenzo-p-dioxin/dibenzofurans(PCDD/Fs), has been well-documented to occur via radical–radical coupling reactions from chlorinated thiophenol precursors. However, the current understanding of the formation mechanism of PCDT/TAs is exclusively limited to the inherent point of view that chlorothiophenoxy radicals act as the only required intermediates for PCDT/TAs. This study investigates reaction pathways for the formation of PCDT/TAs involving two new types of radical species, i.e., substituted phenyl radicals and substituted thiophenoxyl diradicals. Taking 2-chlorothiophenol(2-CTP) as a model compound for chlorothiophenols,we found that apart from the mostly discussed chlorothiophenoxy radicals, substituted phenyl radicals and substituted thiophenoxyl diradicals could also be readily formed via the reaction of 2-CTP with H radicals. Furthermore, direct self-and cross-coupling of these radicals can result in the formation of PCDT/TAs, including 1-monochlorothianthrene(1-MCTA), 1,6-dichlorothianthrene(1,6-DCTA), 4,6-dichlorodibenzothiophene(4,6-DCDT)and 1,6-dichlorodibenzothiophene(1,6-DCDT). The pathways proposed in this work are proven to be both thermodynamically and kinetically favorable. Particularly, comparisons were made between the formation mechanisms of sulfurated and oxygenated dioxin systems from an energetic point view, showing that replacing oxygen with sulfur atoms greatly reduces the activation barriers of the rate-controlling steps involved in the PCDT/TA formation processes compared with those involved for PCDD/Fs. The calculated results in this work may improve our understanding of the formation mechanism of PCDT/TAs from chlorothiophenol precursors and should be informative to environmental scientists.展开更多
Benzo[1,2-c;4,5-cʹ]bis[1,2,5]thiadiazole(BBT)has intrinsic diradical character and herein it is used to construct organic near-infrared(NIR)dyes together with the aromatic porphyrin unit.Three BBT-porphyrin hybrid dye...Benzo[1,2-c;4,5-cʹ]bis[1,2,5]thiadiazole(BBT)has intrinsic diradical character and herein it is used to construct organic near-infrared(NIR)dyes together with the aromatic porphyrin unit.Three BBT-porphyrin hybrid dyes 1-3 with different linkage modes are synthesized by Pd-catalyzed Sonogashira crosscoupling between meso-ethynylene porphyrin units and monobromo-/dibromo-BBT,or through unexpected homocoupling between the BBT units.They all possess small open-shell diradical character and display intense NIR absorption in the range of 800-1000 nm.They also exhibit amphoteric redox behavior.BBT-based diradicaloids are thus good candidates for organic NIR dyes.展开更多
基金Natural Science Foundation of Shandong Province,China(Nos.ZR2016BL13 and ZR2015EQ021)National Natural Science Foundation of China(No.51505065)Foundation for Science and Technology of Shandong Provincial Universities,China(No.J16LC55)。
文摘The parent and radical-modified chitin units are computationally studied and the parent chitin unit possesses closed-shell singlet(CS)state as its ground state.Two radicals(CH_(3)·and CH_(3)CH_(2)·)are chosen to modify the parent chitin unit.Calculations predict that CH_(3)CH_(2)·-modified chitin unit possesses the open-shell broken-symmetry(BS)singlet diradical ground state,different from that CH_(3)·-modified chitin unit is a triplet diradical.That is to say,the magnetic conversion can occur from nonmagnetic exchange coupling to antiferromagnetic(AFM)or ferromagnetic(FM)exchange coupling by means of the radical modification method.The present work helps to get a basic understanding of structures and electronic properties of chitin and its radical-modified derivatives at the atomistic level.Moreover,it also provides a feasible way to design new chitin-based magnetic materials and organic magnetic switches.
基金Supported by the National Natural Science Foundation of China(No.20873017)the Natural Science Foundation of Jilin Province,China(No.20101154)
文摘The polarizability(α) and second hyperpolarizability(γ) were systemically investigated for singlet diradical complex involving X(X=B,Al,Ga) atom.The results show that both the α and γ can be effectively tuned by varying the distance R(between compound A and a water molecule) and acceptor atom X.The lone pair of electrons from the O atom of the water molecule entered into the vacant p orbital of atom X,which increased the diradical character and led to the increase of the α and γ values.Furthermore,the polarizable continuum model(PCM) was used to test the effects of H2O and CCl4 solvents on the α and γ values.Both the α and γ values of the studied diradical complex 1a(1b,1c) in H2O and CCl4 were uniformly enhanced.And the solvent effects of H2O on either α or γ were larger than those of CCl4.
基金the JSPS for KAKENHI funding(Grant No.JP21H01918 and JP20K21194)a Grant-in-Aid for Transformative Research Areas(A)“Condensed Conjugation”(JSPS for KAKENHI funding Grant No.JP20H05865)from MEXT,Japan.
文摘Knowledge about electronic structures is important to gain an understanding of the unique functional properties of diradicaloids.In this study,we synthesized and characterized a diradicaloid in which two phenalenyl radical sites are coupled antiferromagnetically via a through-space interaction.The results of quantum chemical,physicochemical(^(1)H NMR,electronic absorption,cyclic voltammetry,SQUID,ESR),and chemical reactivity studies show that this diradicaloid has singlet diradical character.An assessment of the nature of the bonding interaction between two radical sites in this species using DFT calculations demonstrates that a small spatial overlap between the two SOMOs in this diradicaloid provides an efficient electron exchange path for the singlet state to be substantially lower in energy than the triplet state.
基金National Natural Science Foundation of China(No.22175074)Jilin Scientific and Technological Development Program,China(No.20220101054JC).
文摘Organic diradicaloids have unusual open-shell nature and properties and are promising materials for organic electronics,spintronics,energy storage and nonlinear optics.In this review,we focus on indeno-type organic diradicaloids and summarize their molecular design and synthesis,as well as topological structures,open-shell characters and diradical properties.The molecular systems are classified into indenofluorenes and diindenoacenes,indeno-based molecules with one-dimensional,two-dimensional and unique topological structures,and heterocyclic indeno-based molecules.By constructing these various topologicalπ-skeletons with tunable conjugation modes and variation of atomic composition,their key open-shell parameters,such as diradical characters and singlet-triplet energy gaps,along with the optical,electronic and magnetic properties,as well as stabilities are efficiently modulated.More attention may be paid to accurate computational analysis,rational design and synthesis,and novel functions of indeno-type diradicaloids,which will promote the development of radical chemistry and materials.
基金National Natural Science Foundation of China(No.52203134)Open Research Fund of State Key Laboratory of Southwestern Chinese Medicine Resources(Chengdu University of Traditional Chinese Medicine),China(No.SKLTCM2022014)+1 种基金partially supported by Grant SCITLAB(No.20012)of Intelligent Terminal Key Laboratory of Sichuan Province and Guangdong Basic,Intelligent Terminal Key Laboratory of Sichuan Province(No.SCITLAB-20013)Applied Basic Research Foundation(No.2021A1515110431).
文摘Organic radicals with unpaired electrons have shown great semiconducting properties with potential applications in the field of organic photodetectors,organic light-emitting diodes and organic spintronics.A major problem for limiting radicals from laboratory research to practical applications is the relatively low chemical and physical stabilities.Therefore,the right selection of radical core is the key to meaningful scientific research.Phenoxyl radical is one of the few stable radicals with spin distribution properties.Moreover,phenoxyl diradicals provide extract stability due to multiple resonance structures.Due to the long-distance spin distribution,which makes phenoxyl diradicals show interesting electronic and magnetic properties.In this review,we summarize the progress of phenoxyl diradicals in recent years in terms of syntheses,properties and future perspective.
文摘Two-electron oxidations of three 1,2-di(bisphenylamino)-benzenes afforded a class of nitrogen analogues of o-quinodimethane. Their elec-tronic structures in the ground state were studied by spectroscopic techniques including EPR and UV-vis absorption spectroscopy. They have open-shell singlet ground states with thermally accessible triplet states. One of them (12+2) has been crystalized and isolated. SQUID measurements, single crystal X-ray diffraction and theoretical calculat ons show I has unexpected non-Kekule diradical character, sharply different from o-quinodirnethane.
基金supported by the National Natural Science Foundation of China(21525102,2169002)the Natural Science Foundation of Jiangsu Province(BK20140014)
文摘By using weakly coordinating anions we succeeded in the stabilization and isolation of two Würster's blue-based diradicaloid dications with saturated spacers. Their geometries and electronic structures were investigated by various experiments in conjunction with DFT calculations. Both one-dimensional alkylate-bridged dications show considerable diradical character with spacer-dependent singlet-triplet energy gaps. One of them displays a much enhanced diradical character and could basically be viewed as a pure diradical with degeneracy of singlet and triplet states.
基金The work was supported by the NSFC(grant nos.51925306,21774130,and 21905277)National Key R&D Program of China(grant no.2018FYA 0305800)+2 种基金Key Research Program of the Chinese Academy of Sciences(grant no.XDPB08-2)the Strategic Priority Research Program of Chinese Academy of Sciences(grant no.XDB28000000)Fundamental Research Funds for the Central University.DFT results described in this short communication are obtained on the National Super-computing Center in Shenzhen(Shenzhen Cloud Computing Center).
文摘Air stable diradicaloid polycyclic aromatic hydrocarbon(PAH)materials possess unique electronic and magnetic properties for various applications.In general,long conjugated distances between two radical centers are required to improve the air stability,thereby complicating the synthetic procedures.Herein,the chalcogen containing rubicenes(O-,S-,and Se-rubicenes)were systematically investigated to understand the chalcogen effects on chalcogen-rubicene physicochemical properties.Impressively,these rubicenes presented unprecedented diradical characterwithin one simple benzene ring and excellent air stabilities.Theirdiradicalcharacterweremanifested by single-crystal X-ray studies,variable-temperature nuclear magnetic resonance,and electron spin resonance.Furthermore,the nucleus independent chemical shifts andthe anisotropy of the induced currentdensity calculations revealed that the formation of diradical was caused by a pro-aromaticity driving force.Importantly,the diradical character of rubicenes are visualizedbyFractionalOccupationNumberWeighted Electron Density(FOD)plots,which present high NFOD values from 1.651 to 1.830.This contribution provided distinctive insights into the structure and property relationship of PAH diradicals.
文摘The mechanism of photocycloaddition reaction between 6-azauracll and acetone was studied by using semiemptrical SCFMO AMI method. It was found that this reaction is not a concerted one. The calculated results are as follows:(1) A T1 state exciplex is on the T1 state energy surface; (2) T exciplex as a reactant will proceed along the energy surface of T1 state to form a diradical intermediate. The energy barrier of this reaction step is 63. 6 kJ/mol; (3) The T1 state diradical intermediate happens to be close in energy to the ground state intermediate with a similar geometry. Such a situation turns out to be very favorable for an intersystem crossing (jump from the T, state to the ground state) ; (4) The final product will be formed from the ground S0 state intermediate via an energy barrier 88. 2 kJ/mol.
基金We thank the National Natural Science Foundation of China(grant nos.22050005,21732004,and 21821001)the Tsinghua University Initiative Scientific Research Program(grant no.2019Z07L01004)for generous financial support.
文摘Recent years have witnessed breakthroughs in the study of zigzag hydrocarbon belts.However,the synthesis of heterocycle-containing zigzag molecular belts remains very rare and challenging despite their interesting structures and potential applications in chemistry and materials science.Here,we report the expeditious construction of a highly strained belt[4]arene[4](1,4-dihydropyridine)structure using the fjords-stitching strategy.The synthesis comprised four-fold abnormal m-bromination of four Npivaloylaniline units and Pd_(2)(dba)_(3)/4-Me_(2)NC_(6)H_(4)Pt Bu_(2)-catalyzed intramolecular C-N bond-forming reactions.Subsequent functionalization through Narylations produced a variety of tetraza-embedded octahydrobelt[8]arenes.Further oxidation of p-methoxyphenyl-substituted belt[4]arene[4](1,4-dihydropyridine)with Ag[Al(O^(t)Bu^(F))^(4)]yielded a singlet diradical dication N-doped zigzag belt.
基金Innovation Program of Shanghai Municipal Education Commission(No.2019-01-07-00-05-E00012)Program for Changjiang Scholars and Innovative Research Team in University for financial support+1 种基金the financial supports sponsored by Shanghai Sailing Program(No.19YF1412900)the Fundamental Research Funds for the Central Universities。
文摘An unexpected bistricyclic aromatic ene AF was synthesized in a tin(Ⅱ)chloride-mediated reductive aromatization reaction.The obtained AF showed a highly overcrowded structural conformation as revealed by X-ray crystallography.Interestingly,AF exhibited reversible high-contrast mechanochromism and thermochromism between pale and red color.The obvious chromism is likely ascribed to the conformation transformation and trace amount of diradical species formation upon stimulus.
基金Supported by the National Natural Science Foundation of China (Grant Nos. 20625309 and 20433020)the National Basic Research Program (Grant No. 2004CB719901)+1 种基金the Ministry of Education of China (Grant No. NCET-04-0450) Fok Ying Tong Education Foundation (Grant No. 91014)
文摘The block correlated coupled cluster (BCCC) method, with the complete active-space self-consistent-field (CASSCF) reference function, has been applied to investigating the singlet-triplet gaps in several substituted carbenes including four halocarbenes (CHCl, CF2, CCl2, and CBr2) and two hydroxycar-benes (CHOH and C(OH)2). A comparison of our results with the experimental data and other theoretical estimates shows that the present approach can provide quantitative descriptions for all the studied carbenes. It is demonstrated that the CAS-BCCC method is a promising theoretical tool for calculating the electronic structures of diradicals.
基金supported by the National Natural Science Foundation (Nos. 21407167, 21621064, and 21607168)the Chinese Academy of Sciences (No. XDB14030500)
文摘Homogeneous formation of polychlorinated dibenzothiophenes/thianthrenes(PCDT/TAs),sulfurated compounds analogous to polychlorinated dibenzo-p-dioxin/dibenzofurans(PCDD/Fs), has been well-documented to occur via radical–radical coupling reactions from chlorinated thiophenol precursors. However, the current understanding of the formation mechanism of PCDT/TAs is exclusively limited to the inherent point of view that chlorothiophenoxy radicals act as the only required intermediates for PCDT/TAs. This study investigates reaction pathways for the formation of PCDT/TAs involving two new types of radical species, i.e., substituted phenyl radicals and substituted thiophenoxyl diradicals. Taking 2-chlorothiophenol(2-CTP) as a model compound for chlorothiophenols,we found that apart from the mostly discussed chlorothiophenoxy radicals, substituted phenyl radicals and substituted thiophenoxyl diradicals could also be readily formed via the reaction of 2-CTP with H radicals. Furthermore, direct self-and cross-coupling of these radicals can result in the formation of PCDT/TAs, including 1-monochlorothianthrene(1-MCTA), 1,6-dichlorothianthrene(1,6-DCTA), 4,6-dichlorodibenzothiophene(4,6-DCDT)and 1,6-dichlorodibenzothiophene(1,6-DCDT). The pathways proposed in this work are proven to be both thermodynamically and kinetically favorable. Particularly, comparisons were made between the formation mechanisms of sulfurated and oxygenated dioxin systems from an energetic point view, showing that replacing oxygen with sulfur atoms greatly reduces the activation barriers of the rate-controlling steps involved in the PCDT/TA formation processes compared with those involved for PCDD/Fs. The calculated results in this work may improve our understanding of the formation mechanism of PCDT/TAs from chlorothiophenol precursors and should be informative to environmental scientists.
基金supported by NRF(NRF-NRFI05-2019-0005)MOE Tier 2 grant(MOE2018-T2-2-094).
文摘Benzo[1,2-c;4,5-cʹ]bis[1,2,5]thiadiazole(BBT)has intrinsic diradical character and herein it is used to construct organic near-infrared(NIR)dyes together with the aromatic porphyrin unit.Three BBT-porphyrin hybrid dyes 1-3 with different linkage modes are synthesized by Pd-catalyzed Sonogashira crosscoupling between meso-ethynylene porphyrin units and monobromo-/dibromo-BBT,or through unexpected homocoupling between the BBT units.They all possess small open-shell diradical character and display intense NIR absorption in the range of 800-1000 nm.They also exhibit amphoteric redox behavior.BBT-based diradicaloids are thus good candidates for organic NIR dyes.